Vibrating device and image equipment having the same

ABSTRACT

A vibrating device includes a dust-screening member and a vibrating member. The dust-screening member is disposed in front of an image surface of an image forming element having the image surface in which an optical image is generated. The dust-screening member has a box shape with about the same small plate thickness as a whole, and includes, in a bottom surface portion of the box shape, a transparent part which spreads from the center of the bottom surface portion. The vibrating member is disposed outside the transparent part of the dust-screening member. The vibrating member is configured to generate, in the bottom surface portion of the dust-screening member, vibration having a vibrational amplitude which is vertical to the bottom surface portion thereof.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromprior Japanese Patent Application No. 2010-198106, filed Sep. 3, 2010,the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to image equipment having image formingelements such as an image sensor element or a display element, and alsoto a vibrating device designed to vibrate the dust-screening member thatis arranged at the front of each image forming element of such an imageequipment.

2. Description of the Related Art

As image equipment having image forming elements, there is known animage acquisition apparatus that has an image sensor element configuredto produce a video signal corresponding to the light applied to itsphotoelectric conversion surface. Also known is an image projector thathas a display element, such as liquid crystal element, which displays animage on a screen. In recent years, image equipment having such imageforming elements have been remarkably improved in terms of imagequality. If dust adheres to the surface of the image forming elementsuch as the image sensor element or display element or to the surface ofthe transparent member (optical element) that is positioned in front ofthe image forming element, the image produced will have shadows of thedust particles. This makes a great problem.

For example, digital cameras of called “lens-exchangeable type” havebeen put to practical use, each comprising a camera body and aphotographic optical system removably attached to the camera body. Thelens-exchangeable digital camera is so designed that the user can usevarious kinds of photographic optical systems, by removing thephotographic optical system from the camera body and then attaching anyother desirable photographic optical system to the camera body. When thephotographic optical system is removed from the camera body, the dustfloating in the environment of the camera flows into the camera body,possibly adhering to the surface of the image sensor element or to thesurface of the transparent member (optical element), such as a lens,cover glass or the like, that is positioned in front of the image sensorelement. The camera body contains various mechanisms, such as a shutterand a diaphragm mechanism. As these mechanisms operate, they producedust, which may adhere to the surface of the image sensor element aswell.

Projectors have been put to practical use, too, each configured toenlarge an image displayed by a display element (e.g., CRT or liquidcrystal element) and project the image onto a screen so that theenlarged image may be viewed. In such a projector, too, dust may adhereto the surface of the display element or to the surface of thetransparent member (optical element), such as a lens, cover glass or thelike, that is positioned in front of the display element, and enlargedshadows of the dust particles may inevitably be projected to the screen.

Various types of mechanisms that remove dust from the surface of theimage forming element or the transparent member (optical element) thatis positioned in front of the image sensor element, provided in suchimage equipment have been developed.

In an electronic image acquisition apparatus disclosed in, for example,U.S. 2004/0169761 A1, a ring-shaped piezoelectric element (vibratingmember) is secured to the circumferential edge of a glass plat shapedlike a disc (dust-screening member). When a voltage of a prescribedfrequency is applied to the piezoelectric element, the glass plat shapedlike a disc undergoes a standing-wave, bending vibration having nodes atthe concentric circles around the center of the glass plat shaped like adisc. This vibration removes the dust from the glass disc. The vibration(vibrational mode 1) produced by the voltage of the prescribed frequencyis a standing wave having nodes at the concentric circles around thecenter of the disc. The dust particles at these nodes cannot be removed,because the amplitude of vibration at the nodes is small. In view ofthis, the glass plat shaped like a disc is vibrated at a differentfrequency, achieving a standing-wave vibration (vibrational mode 2) thathas nodes at concentric circles different from those at which the nodesof vibrational mode 1 are located. Thus, those parts of the glass disc,where the nodes lie in vibrational mode 1, are vibrated at largeamplitude.

Jpn. Pat. Appln. KOKAI Publication No. 2007-228246 discloses arectangular dust-screening member and piezoelectric elements secured tothe opposite sides of the dust-screening member, respectively. Thepiezoelectric elements produce vibration at a predetermined frequency,resonating the dust-screening member. Vibration is thereby achieved insuch mode that nodes extend parallel to the sides of the dust-screeningmember. Further, as in the mechanism of U.S. 2004/0169761 A1, thedust-screening member is made to resonate at a different frequency,accomplishing a standing-wave vibrational mode, in order to change theopposition of nodes. Any one of these vibrational modes achieves bendingvibration having nodes extending parallel to the sides of thedust-screening member.

BRIEF SUMMARY OF THE INVENTION

According to a first aspect of the present invention, there is provideda vibrating device comprising:

a dust-screening member disposed in front of an image surface of animage forming element having the image surface in which an optical imageis generated, the dust-screening member having a box shape with aboutthe same small plate thickness as a whole, and including, in a bottomsurface portion of the box shape, a transparent part which spreads fromthe center of the bottom surface portion; and

a vibrating member disposed outside the transparent part of thedust-screening member and configured to generate, in the bottom surfaceportion of the dust-screening member, vibration having a vibrationalamplitude which is vertical to the bottom surface portion thereof.

According to a second aspect of the present invention, there is providedan image equipment comprising:

an image forming element having an image surface in which an opticalimage is generated;

a dust-screening member disposed in front of the image surface of theimage forming element, the dust-screening member having a box shape withabout the same small plate thickness as a whole, and including, in abottom surface portion of the box shape, a transparent part whichspreads from the center of the bottom surface portion;

a vibrating member disposed outside the transparent part of thedust-screening member and configured to generate, in the bottom surfaceportion of the dust-screening member, vibration having a vibrationalamplitude which is vertical to the bottom surface portion thereof; and

a sealing structure portion configured to seal a space portion on theside of circumferential edges of the image forming element and thedust-screening member and to constitute the sealed space portion in aportion where both the image forming element and the dust-screeningmember are formed to face each other.

According to a third aspect of the present invention, there is provideda vibrating device comprising:

a dust-screening member disposed in front of an image surface of animage forming element having the image surface in which an optical imageis generated, the dust-screening member being configured to have a boxshape which includes a bottom surface portion having a lighttransmitting part through which one of light coming from the imageforming element and light coming into the image forming elementtransmits, and side wall portions which tilt as much as a predeterminedangle and extend from all end face portions of the bottom surfaceportion in a direction of the image forming element, and is formed sothat at least the bottom surface portion has a substantially uniformsmall thickness; and

a vibrating member disposed in one of a position of the dust-screeningmember other than the light transmitting part of the bottom surfaceportion and a flat surface portion of the side wall portion, andconfigured to apply, to the bottom surface portion of the dust-screeningmember, a vibrational amplitude which is vertical to the bottom surfaceportion thereof.

According to a fourth aspect of the present invention, there is providedan image equipment comprising:

an image forming unit including an image forming element having an imagesurface in which an optical image is generated;

a dust-screening member disposed in front of an image surface of theimage forming element, the dust-screening member being configured tohave a box shape which includes a bottom surface portion having a lighttransmitting part through which one of light coming from the imageforming element and light coming into the image forming elementtransmits, and side wall portions which tilt as much as a predeterminedangle and extend from all end face portions of the bottom surfaceportion in a direction of the image forming element, and is formed sothat at least the bottom surface portion has a substantially uniformsmall thickness;

a vibrating member disposed in one of a position of the dust-screeningmember other than the light transmitting part of the bottom surfaceportion and a flat surface portion of the side wall portion, andconfigured to apply, to the bottom surface portion of the dust-screeningmember, a vibrational amplitude which is vertical to the bottom surfaceportion thereof; and

a sealing structure portion configured to constitute a sealed spaceportion in a portion where both the image forming unit and thedust-screening member are formed to face each other.

Advantages of the invention will be set forth in the description whichfollows, and in part will be obvious from the description, or may belearned by practice of the invention. The advantages of the inventionmay be realized and obtained by means of the instrumentalities andcombinations particularly pointed out hereinafter.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate embodiments of the invention, andtogether with the general description given above and the detaileddescription of the embodiments given below, serve to explain theprinciples of the invention.

FIG. 1 is a block diagram schematically showing an exemplary systemconfiguration, mainly electrical, of a lens-exchangeable, single-lenselectronic camera (digital camera) that is a first embodiment of theimage equipment according to this invention;

FIG. 2A is a vertical side view of an image sensor element unit of thedigital camera, which includes a dust removal mechanism (or a sectionalview taken along line A-A shown in FIG. 2B);

FIG. 2B is a front view of the dust removal mechanism, as viewed fromthe lens side;

FIG. 3A is a perspective view showing a major component (vibrator) ofthe dust removal mechanism;

FIG. 3B is a sectional view of the major component, taken along line B-Bshown in FIG. 3A;

FIG. 4A is a front view of a dust filter, explaining how the dust filteris vibrated;

FIG. 4B is a sectional view of the dust filter, taken along line B-Bshown in FIG. 4A;

FIG. 4C is a sectional view of the dust filter, taken along line C-Cshown in FIG. 4A;

FIG. 5 is a diagram explaining how the dust filter is vibrated inanother mode;

FIG. 6 is a diagram explaining the concept of vibrating the dust filter;

FIG. 7 is a diagram showing another configuration the dust filter mayhave;

FIG. 8 is a diagram showing still another configuration the dust filtermay have;

FIG. 9 is a diagram showing another configuration the dust filter mayhave;

FIG. 10 is a diagram showing still another configuration the dust filtermay have;

FIG. 11 is a conceptual diagram of the dust filter, explaining thestanding wave that is produced in the dust filter;

FIG. 12 is a circuit diagram schematically showing the configuration ofa dust filter control circuit;

FIG. 13 is a timing chart showing the signals output from the componentsof the dust filter control circuit;

FIG. 14A is the first part of a flowchart showing an exemplary camerasequence (main routine) performed by the microcomputer for controllingthe digital camera body according to the first embodiment;

FIG. 14B is the second part of the flowchart showing the exemplarycamera sequence (main routine);

FIG. 15 is a flowchart showing the operating sequence of “silentvibration” that is a subroutine shown in FIG. 14A;

FIG. 16 is a flowchart showing the operation sequence of the “displayprocess” performed at the same time Step S201 of “silent vibration,”i.e. subroutine (FIG. 15), is performed;

FIG. 17 is a flowchart showing the operating sequence of the “displayprocess” performed at the same time Step S203 of “silent vibration,”i.e., or subroutine (FIG. 15), is performed;

FIG. 18 is a flowchart showing the operating sequence of the “displayprocess” performed at the same time Step S205 of “silent vibration,”i.e., subroutine (FIG. 15), is performed;

FIG. 19 is a diagram showing the form of a resonance-frequency wavecontinuously supplied to vibrating members during silent vibration; and

FIG. 20 is a flowchart showing the operating sequence of “silentvibration,” i.e., subroutine in the operating sequence of the digitalcamera that is a second embodiment of the image equipment according tothe present invention.

DETAILED DESCRIPTION OF THE INVENTION

Best modes of practicing this invention will be described with referenceto the accompanying drawings.

First Embodiment

An image equipment according to this invention, which will beexemplified below in detail, has a dust removal mechanism for the imagesensor element unit that performs photoelectric conversion to produce animage signal. Here, a technique of improving the dust removal functionof, for example, an electronic camera (hereinafter called “camera” willbe explained. The first embodiment will be described, particularly inconnection with a lens-exchangeable electronic camera (digital camera),with reference to FIGS. 1 to 2B.

First, the system configuration of a digital camera 10 according to thisembodiment will be described with reference to FIG. 1. The digitalcamera 10 has a system configuration that comprises body unit 100 usedas camera body, and a lens unit 200 used as an exchange lens, i.e., oneof accessory devices.

The lens unit 200 can be attached to and detached from the body unit 100via a lens mount (not shown) provided on the front of the body unit 100.The control of the lens unit 200 is performed by the lens-controlmicrocomputer (hereinafter called “Lucom”) 201 provided in the lens unit200. The control of the body unit 100 is performed by the body-controlmicrocomputer (hereinafter called “Bucom” 101 provided in the body unit100. By a communication connector 102, the Lucom 210 and the Bucom 101are electrically connected to each other, communicating with each other,while the lens unit 200 remains attached to the body unit 100. The Lucom201 is configured to cooperate, as subordinate unit, with the Bucom 101.

The lens unit 200 further has a photographic lens 202, a diaphragm 203,a lens drive mechanism 204, and a diaphragm drive mechanism 205. Thephotographic lens 202 is driven by a stepping motor (not shown) that isprovided in the lens drive mechanism 204. The diaphragm 203 is driven bya stepping motor (not shown) that is provided in the diaphragm drivemechanism 205. The Lucom 201 controls these motors in accordance withthe instructions made by the Bucom 101.

In the body unit 100, a shutter 108, a shutter cocking mechanism 112,and a shutter control circuit 113 are arranged as shown in FIG. 1. Theshutter 108 is a focal plane shutter arranged on the photographicoptical axis. The shutter cocking mechanism 112 biases the spring (notshown) that drives the front curtain and rear curtain of the shutter108. The shutter control circuit 113 controls the motions of the frontcurtain and rear curtain of the shutter 108.

In the body unit 100, an image acquisition unit 116 is further providedalong a photographic optical axis to perform photoelectric conversion onthe image of an object, which has passed through the above-mentionedoptical system. The image acquisition unit 116 is constituted as a unitby integrating an image forming unit and a dust filter 119 which is adust-screening member, via a holder 145. The image forming unit includesa CCD 117 that is an image sensor element as an image forming element,and an optical low-pass filter (LPF) 118 that is arranged in front ofthe CCD 117. Here, the optical low-pass filter (LPF) 118 is an opticalelement made of quartz crystal or the like. The dust filter 119 is anoptical element made of quartz crystal, glass or the like, and may bemade of a transparent plastic material. That is, the dust filter 119 maybe a box-like transparent member which can be vibrated.

On one side of the circumferential edge of the dust filter 119, apiezoelectric element 120 is attached. The piezoelectric element 120 hastwo electrodes. A dust filter control circuit 121, which is a driveunit, drives the piezoelectric element 120 at the frequency determinedby the size and material of the dust filter 119. As the piezoelectricelement 120 vibrates, the dust filter 119 undergoes specific vibration.Dust can thereby be removed from the surface of the dust filter 119. Tothe image acquisition unit 116, an anti-vibration unit is attached tocompensate for the motion of the hand holding the digital camera 10.

The digital camera 10 according to this embodiment further has a CCDinterface circuit 122, a liquid crystal monitor 123, an SDRAM 124, aFlash ROM 125, and an image process controller 126, thereby to performnot only an electronic image acquisition function, but also anelectronic record/display function. The electronic image acquisitionfunction includes a so-called through image display function, whichdisplays an image acquired by the CCD 117 as a moving image on theliquid crystal monitor 123, and uses it as a viewfinder, and a movingimage recording function which records a moving image. As a viewfinderfunction, an optical single-lens reflex viewfinder or the like may beprovided. The CCD interface circuit 122 is connected to the CCD 117. TheSDRAM 124 and the Flash ROM 125 function as storage areas. The imageprocess controller 126 uses the SDRAM 124 and the Flash ROM 125, toprocess image data. A recording medium 127 is removably connected by acommunication connector (not shown) to the body unit 100 and cantherefore communicate with the body unit 100. The recording medium 127is an external recording medium, such as one of various memory cards oran external HDD, and records the image data acquired by photography. Asanother storage area, a nonvolatile memory 128, e.g., EEPROM, isprovided and can be accessed from the Bucom 101. The nonvolatile memory128 stores prescribed control parameters that are necessary for thecamera control.

To the Bucom 101, there are connected an operation display LCD 129, anoperation display LED 130, a camera operation switch 131, and a flashcontrol circuit 132. The operation display LCD 129 and the operationdisplay LED 130 display the operation state of the digital camera 10,informing the user of this operation state. The operation display LED129 or the operation display LED 130 has, for example, a display unitconfigured to display the vibration state of the dust filter 119 as longas the dust filter control circuit 121 keeps operating. The cameraoperation switch 131 is a group of switches including, for example, arelease switch, a mode changing switch, a power switch, which arenecessary for the user to operate the digital camera 10. The flashcontrol circuit 132 drives a flash tube 133.

In the body unit 100, a battery 134 used as power supply and apower-supply circuit 135 are further provided. The power-supply circuit135 converts the voltage of the battery 134 to a voltage required ineach circuit unit of the digital camera 10 and supplies the convertedvoltage to the each circuit unit. In the body unit 100, too, a voltagedetecting circuit (not shown) is provided, which detects a voltagechange at the time when a current is supplied from an external powersupply though a jack (not shown).

The components of the digital camera 10 configured as described aboveoperate as will be explained below. The image process controller 126controls the CCD interface circuit 122 in accordance with theinstructions coming from the Bucom 101, whereby image data is acquiredfrom the CCD 117. The image data is converted to a video signal by theimage process controller 126. The image represented by the video signalis displayed by the liquid crystal monitor 123. Viewing the imagedisplayed on the liquid crystal monitor 123, the user can confirm theimage photographed.

The SDRAM 124 is a memory for temporarily store the image data and isused as a work area in the process of converting the image data. Theimage data is held in the recording medium 127, for example, after ithas been converted to JPEG data. Here, when image data is for a movingimage, it is converted into MPEG data.

The photographic lens 202 is focused as follows. Images are acquired bysequentially changing the position of the photographic lens 202. Amongthe acquired images, a position with the highest contrast is calculatedby the Bucom 101. This position is transmitted from the Bucom 101 to theLucom 201 through the communication connector 102. The Lucom 201controls the photographic lens 202 to this position. As for photometricmeasurement, know measurement is performed based on the amount of lightdetected from an acquired image.

The image acquisition unit 116 that includes the CCD 117 will bedescribed with reference to FIGS. 2A and 2B. Note that the hatched partsshown in FIG. 2B show the shapes of members clearly, not to illustratingthe sections thereof.

As described above, the image acquisition unit 116 has the CCD 117, theoptical LPF 118, the dust filter 119, and the piezoelectric element 120.The CCD 117 is an image sensor element that produces an image signalthat corresponds to the light applied to its photoelectric conversionsurface through the photographic optical system. The optical LPF 118 isarranged at the photoelectric conversion surface of the CCD 117 andremoves high-frequency components from the light beam coming from theobject through the photographic optical system. The dust filter 119 is abox-like dust-screening member arranged in front of the optical LPF 118and facing the optical LPF 118, spaced apart therefrom by apredetermined distance. The piezoelectric element 120 is arranged on aside wall portion of the box-like dust filter 119 and is a vibratingmember for applying specific vibration to the dust filter 119.

The CCD chip 136 of the CCD 117 is mounted directly on a flexiblesubstrate 137 that is arranged on a fixed plate 138. From the ends ofthe flexible substrate 137, connection parts 139 a and 139 b extend.Connectors 140 a and 140 b are provided on a main circuit board 141. Theconnection parts 139 a and 139 b are connected to the connectors 140 aand 140 b, whereby the flexible substrate 137 is connected to the maincircuit board 141. The CCD 117 has a protection glass plate 142. Theprotection glass plate 142 is secured to the flexible substrate 137,with a spacer 143 interposed between it and the flexible substrate 137.

Between the CCD 117 and the optical LPF 118, a filter holding member 144made of elastic material is arranged on the front circumferential edgeof the CCD 117, at a position where it does not cover the effective areaof the photoelectric conversion surface of the CCD 117. The filterholding member 144 abuts on the optical LPF 118, at a part close to therear circumferential edge of the optical LPF 118. The filter holdingmember 144 functions as a sealing member that maintains the junctionbetween the CCD 117 and the optical LPF 118 almost airtight. A holder145 is provided, covering seals the CCD 117 and the optical LPF 118 inairtight fashion. The holder 145 has a rectangular opening 146 in a partthat is substantially central around the photographic optical axis. Theinner circumferential edge of the opening 146, which faces the dustfilter 119, has a stepped part 147 having an L-shaped cross section.Into the opening 146, the optical LPF 118 and the CCD 117 are fittedfrom the back. In this case, the front circumferential edge of theoptical LPF 118 contacts the stepped part 147 in a virtually airtightfashion. Thus, the optical LPF 118 is held by the stepped part 147 at aspecific position in the direction of the photographic optical axis. Theoptical LPF 118 is therefore prevented from slipping forwards from theholder 145. The level of airtight sealing between the CCD 117 and theoptical LPF 118 is sufficient to prevent dust from entering to form animage having shadows of dust particles. In other words, the sealinglevel need not be so high as to completely prevent the in-flow ofgasses.

On the other hand, a front surface side of the holder 145 is providedwith an opening which becomes an image forming light passing area 149.In a circumferential edge of the opening, a fitting portion 150 isformed over the whole periphery thereof. In the fitting portion 150, aninner peripheral wall of a holding member 151 made of a soft materialsuch as a rubber fits. Around the whole periphery of the holding member151, there is formed a groove 152 in which an open end of the thinbox-like dust filter 119 fits. The box-like dust filter 119 fits in thegroove 152 of the holding member 151, and is fixed thereto with anadhesive or the like. On the other hand, the holding member 151 is fixedto the holder 145 with the adhesive or the like, in the fitting portion150 of the holder 145 or the surface of the holding member which isorthogonal to the fitting portion 150. When the open end of the box-likedust filter 119 is fixed to the holder 145 which is a fixing member viathe soft holding member in this manner, the dust filter 119 is held infront of the optical LPF 118, spaced apart therefrom by thepredetermined distance. It is to be noted that the open end of the dustfilter 119 may directly be attached to the holder 145 with the adhesiveor the like, instead of employing such a fixing process.

The holding member 151 is made of a vibration attenuating material suchas a rubber or a resin, not to impede the vibration of the dust filter119. Moreover, a space formed by the dust filter 119 and the LPF 118 issealed from dust by the holding member 151, and hence such dust thatforms an image having shadows of dust particles does not enter thisspace from the outside. Moreover, when a micro droplet, or adhesive dustwhich cannot remarkably easily be removed by the vibration adheres tothe surface of the dust filter 119 on a photographic lens side, acleaning operation by wiping is required. Even in such a case, the dustfilter 119 with the box shape has a sufficient rigidity and does notbreak down, even when an external force is applied thereto during thecleaning operation. The holder 145 formed in a desired size to mount theCCD 117 as an image forming element thereon, the fitting portion 150,and the filter holding member 144 which airtightly holds betweenness ofthe CCD 117 and the optical LPF 118 constitute a sealing structure toseal at the circumferential edges of the CCD 117 and dust filter 119.The image acquisition unit 116 is configured, so that the area formed bythe opposing CCD 117 and dust filter 119 is airtight by the abovesealing structure. The level of airtight sealing between the dust filter119 and the fitting portion 150 is sufficient to prevent dust fromentering to form an image having the shadows of dust particles, so thatthe image can be prevented from being influenced by the dust. Thesealing level need not be so high as to completely prevent the in-flowof gasses.

To the end of the piezoelectric element 120, which is vibrating member,flex 157, i.e., flexible printed board, is electrically connected. Theflex 157 inputs an electric signal (later described) from the dustfilter control circuit 121 to the piezoelectric element 120, causing theelement 120 to vibrate in a specific way. The flex 157 is made of resinand cupper etc., and has flexibility. Therefore, the flex 157 littleattenuates the vibration of the piezoelectric element 120. The flex 157is provided at position where the vibrational amplitude is small (at thenodes of vibration, which will be described later), and can thereforesuppress the attenuation of vibration. The piezoelectric element 120moves relative to the body unit 100 if the camera 10 has such ahand-motion compensating mechanism as will be later described. Hence, ifthe dust filter control circuit 121 is held by a holding member formedintegral with the body unit 100, the flex 157 is deformed and displacedas the hand-motion compensating mechanism operates. In this case, theflex 157 effectively works because it is thin and flexible. In thepresent embodiment, the flex 157 has a simple configuration, extendingfrom one position. It is best fit for use in cameras having ahand-motion compensating mechanism.

The dust removed from the surface of the dust filter 119 falls onto thebottom of the body unit 100, by virtue of the vibration inertia and thegravity. In this embodiment, a base 158 is arranged right below the dustfilter 119, and a holding member 159 made of, for example, adhesivetape, is provided on the base 158. The holding member 159 reliably trapsthe dust fallen from the dust filter 119, preventing the dust frommoving back to the surface of the dust filter 119.

The hand-motion compensating mechanism will be explained in brief. Asshown in FIG. 1, the hand-motion compensating mechanism is composed ofan X-axis gyro 160, a Y-axis gyro 161, a vibration control circuit 162,an X-axis actuator 163, a Y-axis actuator 164, an X-frame 165, a Y-frame166 (holder 145), a frame 167, a position sensor 168, and an actuatordrive circuit 169. The X-axis gyro 160 detects the angular velocity ofthe camera when the camera moves, rotating around the X axis. The Y-axisgyro 161 detects the angular velocity of the camera when the camerarotates around the Y axis. The vibration control circuit 162 calculatesa value by which to compensate the hand motion, from theangular-velocity signals output from the X-axis gyro 160 and Y-axis gyro161. In accordance with the hand-motion compensating value thuscalculated, the actuator drive circuit 169 moves the CCD 117 in theX-axis direction and Y-axis direction, which are first and seconddirections orthogonal to each other in the XY plane that isperpendicular to the photographic optical axis, thereby to compensatethe hand motion, if the photographic optical axis is taken as Z axis.More precisely, the X-axis actuator 163 drives the X-frame 165 in theX-axis direction upon receiving a drive signal from the actuator drivecircuit 169, and the Y-axis actuator 164 drives the Y-frame 166 in theY-axis direction upon receiving a drive signal from the actuator drivecircuit 169. That is, the X-axis actuator 163 and the Y-axis actuator164 are used as drive sources, the X-frame 165 and the Y-frame 166(holder 145) which holds the CCD 117 of the image acquisition unit 116are used as objects that are moved with respect to the frame 167. Notethat the X-axis actuator 163 and the Y-axis actuator 164 are eachcomposed of an electromagnetic motor, a feed screw mechanism, and thelike. Alternatively, each actuator may be a linear motor using a voicecoil motor, a linear piezoelectric motor or the like. The positionsensor 168 detects the position of the X-frame 165 and the position ofthe Y-frame 166. On the basis of the positions the position sensor 168have detected, the vibration control circuit 162 controls the actuatordrive circuit 169, which drives the X-axis actuator 163 and the Y-axisactuator 164. The position of the CCD 117 is thereby controlled.

The dust removal mechanism of the first embodiment will be described indetail, with reference to FIGS. 3A to 11. The dust filter 119 has a thinbox shape. A bottom surface portion 119 a of the box has a shapesurrounded by a curve including a circle, or a polygonal plate-likeshape as a whole (a square plate, in this embodiment). Moreover, in thebottom surface portion 119 a of the dust filter 119, at least, the areaspreading as prescribed from the position obtaining a maximumvibrational amplitude to the radial direction forms a light transmittingpart. Alternatively, the bottom surface portion 119 a of the dust filter119 has a circular shape as a whole, and may be D-shaped, formed bylinearly cutting part of a circular plate, thus defining one side. Stillalternatively, it may be formed in an oval shape by cutting a squareplate, having two opposite sides accurately cut and having upper andlower sides. In this manner, the shape may be a combination of curvesand straight lines. Moreover, the dust filter 119 has side wall portions119 b which tilt as much as a predetermined angle and extend from allend face portions of the bottom surface portion 119 a in a direction ofthe image forming element. The bottom surface portion 119 a and the sidewall portions 119 b form the box-like dust filter 119 in the box shapein which the bottom surface portion 119 a and the side wall portions 119b have a substantially uniform thickness. The above-mentioned fasteningmechanism (a fastening process via the holding member 151 or a processof directly fastening the dust filter 119 to the holder 145 which is thefixing member with the adhesive or the like) fastens the dust filter119, with the light transmitting part opposed to the front of the LPF118 and spaced from the LPF 118 by a predetermined distance. Here, boththe bottom surface portion 119 a and the side wall portions 119 b of thebox-like dust filter 119 may have a uniformly small thickness, or atleast the bottom surface portion 119 a may have the uniformly smallthickness.

Moreover, in a flat surface portion of the bottom surface portion 119 aof the dust filter 119 at a position other than the image forming lightpassing area 149 or in a flat surface portion of the side wall portion119 b (the lower side wall portion 119 b in the present embodiment), thepiezoelectric element 120 is disposed by means of, for example, adhesionusing the adhesive, or the like. The piezoelectric element 120 is thevibrating member for applying the vibration to the bottom surfaceportion 119 a of the dust filter 119. In consequence, a vibrator 170 isformed by arranging the piezoelectric element 120 on the dust filter119. The vibrator 170 undergoes resonance when a voltage of a prescribedfrequency is applied to the piezoelectric element 120. The resonanceachieves such bending vibration of a large amplitude vertically to thebottom surface portion 119 a, as illustrated in FIG. 4A to FIG. 4C.

Here, an angle formed by the each side wall portion 119 b and the bottomsurface portion 119 a constituting the dust filter 119 is preferably 90°or more, when the integral forming of the side wall portion 119 b andthe bottom surface portion 119 a is taken into consideration. Moreover,when the enlargement of a projected area and the rigidity are taken intoconsideration, the angle is preferably set to be about 135° or less.Furthermore, when a surface connecting the bottom surface portion 119 ato the side wall portion 119 b is constituted of a surface which isapproximate to a cylindrical surface as shown in FIG. 3A and FIG. 3B,the rigidity of the dust filter 119 becomes higher, and the dust filter119 can be miniaturized. Furthermore, in the present embodiment, thebottom surface portion 119 a and the side wall portions 119 b of thedust filter 119 are integrally formed, but the portions may beconstituted of separate members joined to each other. On the other hand,only one piezoelectric element 120 is disposed in FIG. 3A and FIG. 3B,but a plurality of piezoelectric elements may be arranged. Moreover, thepiezoelectric element 120 may be disposed on an inner surface of thedust filter 119 (the surface on an image acquisition element side).

As shown in FIG. 3A, signal electrodes 171 and 172 are formed on thepiezoelectric element 120. Note that the hatched parts shown in FIG. 3Ashow the shapes of the signal electrodes clearly, not to illustratingthe sections thereof. The signal electrode 172 is provided on the backopposing the signal electrode 171, and is bent toward that surface ofthe piezoelectric element 120, on which the signal electrode 171 isprovided, along the side wall portion of the piezoelectric element 120.The flex 157 having the above-mentioned conductive pattern iselectrically connected to the signal electrode 171 and signal electrode172. To the signal electrodes 171 and 172, a drive voltage of theprescribed frequency is applied form the dust filter control circuit 121through flex 157. The drive voltage, thus applied, can cause the dustfilter 119 to undergo such a two-dimensional, standing-wave bendingvibration as is shown in FIGS. 4A to 4C. The side wall portion 119 b ofthe dust filter 119 has a long side length LA, and a short side lengthLB orthogonal to the long side. (This size notation accords with thesize notation used in FIGS. 7 to 10.) Since the dust filter 119 shown inFIG. 4A is rectangular, it is identical in shape to the “virtualrectangle” according to this invention (described later). (The long sidelength LA is equal to the side length LF of the virtual rectangle). Thebending vibration shown in FIG. 4A is standing wave vibration. In FIG.4A, the blacker the streaks, each indicating a node area 173 ofvibration (i.e., area where the vibrational amplitude is small), thesmaller the vibrational amplitude is. Note that the meshes shown in FIG.4A are division meshes usually used in the final element method.

If the node areas 173 are at short intervals as shown in FIG. 4A whenthe vibration speed is high, in-plane vibration (vibration along thesurface) will occur in the node areas 173. This vibration induces alarge inertial force in the direction of the in-plane vibration (seemass point Y2 in FIG. 11, described later, which moves over the nodealong an arc around the node, between positions Y2 and Y2′) to the dustat the node areas 173. If the dust filter 119 is inclined to becomeparallel to the gravity so that a force may act along the dust receivingsurface, the inertial force and the gravity can remove the dust from thenode areas 173.

In FIG. 4A, the white areas indicate areas where the vibrationalamplitude is large. The dust adhering to any white area is removed bythe inertial force exerted by the vibration. The dust adhering to a nodearea 173 of the vibration can be removed, when an electric signal havinga different frequency is input into the piezoelectric element 120 toproduce vibration in another vibration mode with another vibrationalamplitude in the node area 173 (e.g. a vibrational mode shown in FIG.5).

The bending vibrational mode shown in FIG. 4A is achieved bysynthesizing the bending vibration of the X-direction and the bendingvibration of the Y-direction. The fundamental state of this synthesis isshown in FIG. 6. By placing the vibrator 170, which has twopiezoelectric elements 120 and 120′ arranged symmetric to the centralaxis X of the dust filter 119, on a member that little attenuatesvibration, such as a foamed rubber block, and then made to vibratefreely, a vibrational mode of producing such lattice-shaped node areas173 as shown in FIG. 6 will be usually attained easily (see Jpn. Pat.Appln. KOKAI Publication No. 2007-228246, identified above). In thefront view of FIG. 6, the broken lines define the node areas 173 (moreprecisely, the lines indicate the positions where the vibrationalamplitude is minimal in the widthwise direction of lines). In this case,a standing wave, bending vibration at wavelength λ_(x) occurs in theX-direction, and a standing wave, bending vibration at wavelength λ_(y)occurs in the Y-direction. These standing waves are synthesized. Withrespect to the origin (x=0, y=0), the vibration Z (x, y) at a givenpoint P (x, y) is expressed by Equation 1, as follows:

Z(x,y)=A·W _(mn)(x,y)·cos(γ)+A·W _(nm)(x,y)·sin(γ)  (1)

where A is amplitude (a fixed value here, but actually changing with thevibrational mode or the power supplied to the piezoelectric elements); mand n are positive integers including 0, indicating the order of naturalvibration corresponding to the vibrational mode; γ is a given phaseangle;

${{W_{mn}\left( {x,y} \right)} = {{\sin \left( {{n\; {\pi \cdot x}} + \frac{\pi}{2}} \right)} \cdot {\sin \left( {{m\; {\pi \cdot y}} + \frac{\pi}{2}} \right)}}};$and${W_{n\; m}\left( {x,y} \right)} = {{\sin \left( {{m\; {\pi \cdot x}} + \frac{\pi}{2}} \right)} \cdot {{\sin \left( {{n\; {\pi \cdot y}} + \frac{\pi}{2}} \right)}.}}$

Assume that the phase angle γ is 0 (γ=0). Then, Equation 1 changes to:

$\begin{matrix}{{Z\left( {x,y} \right)} = {A \cdot {W_{{mn}\;}\left( {x,y} \right)}}} \\{= {A \cdot {\sin \left( {\frac{n \cdot \pi \cdot x}{\lambda_{x\;}} + \frac{\pi}{2}} \right)} \cdot {{\sin \left( {\frac{m \cdot \pi \cdot y}{\lambda_{y}} + \frac{\pi}{2}} \right)}.}}}\end{matrix}$

Further assume that λ_(x)=λ_(y)=λ=1 (x and y are represented by the unitof the wavelength of bending vibration). Then:

$\begin{matrix}{{Z\left( {x,y} \right)} = {A \cdot {W_{mn}\left( {x,y} \right)}}} \\{= {A \cdot {\sin \left( {{n \cdot \pi \cdot x} + \frac{\pi}{2}} \right)} \cdot {{\sin \left( {{m \cdot \pi \cdot y} + \frac{\pi}{2}} \right)}.}}}\end{matrix}$

FIG. 6 shows the vibrational mode that is applied if m=n (since theX-direction vibration and the Y-direction vibration are identical interms of order and wavelength, the dust filter 119 has a square shape).In this vibrational mode, the peaks, nodes and valleys of vibrationappear at regular intervals in both the X-direction and the Y-direction,and vibration node areas 173 appear as a checkerboard pattern(conventional vibrational mode). In the vibrational mode where m=0, n=1,the vibration has peaks, nodes and valleys parallel to a side (side LB)that extends parallel to the Y-direction. In the vibrational modeidentified with a checkerboard pattern or peaks, nodes and valleysparallel to a side, the X-direction vibration and the Y-directionvibration remain independent, never synthesized to increase thevibrational amplitude.

Here, if the dust filter 119 is shaped a little close to a rectangle, avibrational mode with a very large vibrational amplitude can beobtained, even if a piezoelectric element is placed along one side as inthis embodiment. (The maximum amplitude at the same level as at theconventional circular dust filter is generated.) At this time, thevibrational mode will be the mode shown in FIG. 4A is obtained. In thisvibrational mode, though the dust filter 119 is rectangular, the peakridges 174 of vibrational amplitude form closed loops (substantiallycircular in FIG. 4A) around the center of the optical axis.Consequently, a reflected wave coming from a side extending in theX-direction and a reflected wave coming from a side extending in theY-direction are efficiently combined, forming a standing wave. Here, thedust filter 119 has at least one side symmetric to the virtual axispassing through the centroid 119 c, and the piezoelectric element 120 isdisposed so that a centroid of the piezoelectric element 120 is locatedon the virtual axis. The center of the closed loop formed by the peakridges 174 of vibrational amplitude becomes a central vibrating area 175having maximum vibration speed and vibrational amplitude. The centroid175 a of the central vibrating area 175 and the centroid 173 a of anarea surrounded by the node area 173 having almost no verticalvibrational amplitude against the surface formed in the bottom surfaceportion 119 a of the dust filter 119, including the centroid 175 a ofthe central vibrating area 175, are substantially identical andsimilarly located on the above virtual axis. However, since only onepiezoelectric element 120 is disposed, the centroid 175 a of the centralvibrating area 175 is displaced from the centroid 119 c of the dustfilter 119 to a side provided with the piezoelectric element 120.

Here, the centroid of the piezoelectric element 120 does not expand orcontract, even if a driving voltage is applied, and hence thepiezoelectric element 120 is preferably attached so that the centroidthereof is positioned in the node area. On the other hand, since theside wall portion 119 b of the dust filter 119 extends in a direction ofthe amplitude of the generated vibration, a boundary portion between thebottom surface portion 119 a and the side wall portion 119 b on theabove virtual axis does not vibrate but forms the node area 173.Therefore, the piezoelectric element 120 has the centroid thereofdisposed in the above boundary portion on the above virtual axis. Inthis case, when the piezoelectric element 120 is disposed on the bottomsurface portion 119 a of the dust filter 119, the position of thecentroid becomes a position where the vibrational amplitude becomeslarge to a certain degree, even if the element is disposed along a longside in the above boundary portion. This is because the piezoelectricelement 120 has a certain degree of dimension in a short side directionthereof. On the other hand, when the piezoelectric element 120 isdisposed on the side wall portion 119 b of the dust filter 119, theposition of the centroid preferably substantially corresponds to theabove boundary portion, because the piezoelectric element 120 has asmall dimension in a thickness direction.

Moreover, in a case where the open end of the dust filter 119 is an endof the bottom surface portion as shown in FIG. 6 and only onepiezoelectric element 120 is disposed, even when the peak ridges 174 ofthe vibrational amplitude draws a concentric circle, a perfect circularshape cannot easily be obtained. This is because a symmetric shape isnot easily obtained and reflecting conditions are not well set. On theother hand, in the box-like dust filter 119 shown in FIG. 4A to FIG. 4C,the perfect circular shape is drawn. This is because the boundaryportions between the bottom surface portion 119 a and the side wallportion 119 b on the above virtual axis and a virtual axis which isorthogonal to this virtual axis form the node areas 173.

The dust filter 119 of the vibrator 170, shown in FIGS. 4A to 4C, is aglass plate (optical element) having a size of 25.0 mm (X-direction: LA,LF)×24.2 mm (Y-direction: LB)×4.2 mm (Z-direction: H) and a uniformthickness of 0.2 mm. The dust filter 119 is rectangular, having longsides LA (25.0 mm, extending in the X-direction) and short sides LB(24.2 mm). Therefore, the bottom surface portion 119 a of the dustfilter 119 is identical to the “virtual rectangle” according to thisinvention, which has the same area as a member surface of the bottomsurface portion. The piezoelectric element 120 is made of a leadtitanate-zirconate ceramic and has a size of 16.6 mm (X-direction)×2.4mm (Y-direction)×0.6 mm (thickness).

The piezoelectric element 120 is adhered with epoxy-based adhesive tothe dust filter 119, extending along the lower side wall portion 119 b.More specifically, the piezoelectric element 120 extends in theX-direction, and arranged symmetric in the Z-direction, with respect toan axis which is parallel to the X-axis passing through the center ofthe lower side wall portion of the dust filter 119 and an axis which isparallel to the Z-axis. At this time, the resonance frequency in thevibrational mode of FIG. 4A is in the vicinity of 44 kHz. At the centerof the dust filter 119, the central vibrating area 175 having maximalvibration speed and vibrational amplitude can be attained if the dustfilter is shaped like a circle in which the rectangular dust filter 119is inscribed.

Moreover, a vibrational mode of FIG. 5 is a mode generated by changing avibrating frequency of the dust filter 119 shown in FIG. 4A to FIG. 4C.In this vibrational mode, the peak ridges 174 of the vibrationalamplitude continuously positioned substantially in the form ofconcentric circles are formed from one side to the other side disposedto face the one side symmetrically to a certain virtual axis passingthrough the centroid 119 c of the dust filter 119. Here, the center ofeach of the peak ridges 174 substantially having the continuouslyconcentric circle shapes is located on the above virtual axis on a sideopposite to the above other side via the above one side of the dustfilter 119.

FIG. 7 shows a modification of the vibrator 170. The modified vibratoruses a bottom surface portion 119 a of a dust filter 119 having a shapeformed by cutting a part of a plate shaped like a disc, thus definingone side. That is, the modified vibrator 170 uses a D-shaped bottomsurface portion 119 a of the dust filter 119 that has a side symmetricwith respect to the symmetry axis extending in the Y-direction. Thepiezoelectric element 120 is arranged on the surface of the dust filter119, extending parallel to that side and positioned symmetric withrespect to the midpoint of the side (or to a symmetry axis extending inthe Y-direction (the virtual axis)), in the same manner as in theconventional plate-like dust filter (see FIG. 6). So shaped, the dustfilter 119 is more symmetric with respect to its center (regarded as thecentroid 119 c of the dust filter 119), and can more readily vibrate ina state desirable to the present embodiment (the vibrational mode inwhich the vibration peak is generated in the form of the concentriccircle). In addition, the dust filter 119 can be smaller than thecircular one. Furthermore, since the piezoelectric element 120 isarranged parallel to the side, the asymmetry in terms vibration,resulting from the cutting, can be made more symmetric by increasing therigidity. This helps to render the vibration state more desirable. Notethat the long side and short side of the dust filter 119 shown in FIG. 7are as follows. As shown in the drawing, one of the long sides includesthe above one side of the bottom surface portion 119 a of the dustfilter 119, and the other long side facing the above one side isparallel to the above one side, and is one side of the virtual rectangle176 which has the same area as the bottom surface portion 119 a of thedust filter 119. The each short side orthogonal to these sides is a sideof the virtual rectangle 176 which has the same area as the bottomsurface portion 119 a of the dust filter 119. It is to be noted thatalso in the present modification, the piezoelectric element 120 may,needless to say, be disposed on the side wall portion of the box-likedust filter 119 more preferably as described above.

FIG. 8 shows another modification of the vibrator 170. This modifiedvibrator uses a bottom surface portion 119 a of a dust filter 119 havingan oval shape formed by symmetrically cutting a circular plate along twoparallel lines, forming two parallel sides. That is, the modifiedvibrator 170 uses a dust filter 119 that has two sides symmetric withrespect to the symmetry axis extending in the Y-direction. In this case,actuate piezoelectric element 120 is arranged not on the straight sides,but on the curved parts defining a circle. In such a configuration, thepiezoelectric element 120 is arranged, efficiently providing a smallervibrator 170. Note that the long side and short side of the dust filter119 shown in FIG. 8 are the long and short sides of a virtual rectangle176 which has the same area as the bottom surface portion 119 a of thedust filter 119, two opposite sides of which extend along the oppositetwo sides of bottom surface portion 119 a of the dust filter 119,respectively. It is to be noted that also in the present modification,the piezoelectric element 120 may, needless to say, be disposed on theside wall portion of the box-like dust filter 119 more preferably asdescribed above.

FIG. 9 shows still another modification of the vibrator 170. In the samemanner as in the modification shown in FIG. 7, a shape of a bottomsurface portion 119 a of a dust filter 119 has one side formed bycutting part of a disc-like shape. Additionally, in the presentmodification, a piezoelectric element 120 is disposed on a side wallportion 119 b of the dust filter 119 in parallel with one side symmetricwith respect to a symmetry axis in a Y-direction, and symmetrically to amidpoint of the side (the symmetry axis in the Y-direction). Here, thesurface of the dust filter 119 on which the piezoelectric element 120 isdisposed has an angle θ of about 135° between the surface and the bottomsurface portion 119 a. When the dust filter 119 is formed in such ashape, symmetry of the shape of the dust filter 119 with respect to thecenter (this may be regarded as the centroid) of the dust filter becomeshigh, and a vibration state of the present embodiment (a vibrationalmode in which a vibration peak is generated in the form of a concentriccircle) is more easily formed, in the same manner as in the modificationshown in FIG. 7. In addition, the shape of the dust filter 119 becomessmaller than a circular one. Furthermore, since the piezoelectricelement 120 is disposed on the side wall portion 119 b, the bottomsurface portion 119 a of the dust filter 119 is further miniaturized.Moreover, a rigidity of the side wall portion 119 b of the dust filter119 becomes high, and an open end 119 d of the side wall portion 119 bcan securely held by a holding member 151 without being deformed. It isto be noted that in FIG. 9, the angle between the only one surface ofthe side wall portion 119 b on which the piezoelectric element 120 isdisposed and the bottom surface portion 119 a is not the right angle,but an angle between each of the another side wall portions 119 b andthe bottom surface portion 119 a of the dust filter is a right angle.The angle between the each of another cylindrical side wall portions 119b except the above one surface and the bottom surface portion 119 a maybe set to an angle of about 90° to 135°. When the angle is set to belarger than 90°, the shape of the dust filter gradually comes close to adisc shape, and hence the vibrational mode having a concentric peak iseasily generated, whereby strong vibration having a higher vibrationspeed is easily generated. Furthermore, when the dust filter 119 isformed in a box-like shape, the rigidity thereof is raised. If the dustfilter having a plate shape is not accurately supported, the dust filtermight break down during the vibration. Therefore, a plate thickness,which has been set to be about 0.5 mm in the plate shape dust filter,can be set to 0.3 mm or less in the box-like shape dust filter.Consequently, since the thickness of the bottom surface portion 119 a tobe vibrated can be set to be small, the vibration speed can be set to behigher than that generated in the plate shape dust filter. On the otherhand, the side wall portion 119 b constituting the dust filter 119 has ahigh rigidity in a vibrating direction of the bottom surface portion 119a, and almost does not vibrate in the vibrating direction of the bottomsurface portion 119 a. Therefore, the open end 119 d which becomes anattaching surface can securely be held by the holding member 151 withoutbeing deformed, whereby the dust filter 119 can securely be supported.

FIG. 10 shows a further modification of the vibrator 170. In the samemanner as in the modification shown in FIG. 8, a bottom surface portion119 a of a dust filter 119 is formed into an oval shape by symmetricallycutting a disc to obtain two parallel sides. Moreover, the surface ofthe filter including two circles is provided with a slope having anangle of about 135° between the slope and the bottom surface portion 119a, and the filter is formed to be smaller than the dust filter 119 ofFIG. 9. Furthermore, a thickness of the side wall portions 119 b to beprovided with an open end 119 d smoothly increases from the bottomsurface portion 119 a, excluding the side wall portion 119 b on which apiezoelectric element 120 is disposed. Since the thickness of the filteron the side of the open end is large, the fixing of the dust filter 119is stabilized as compared with the dust filter 119 of FIG. 9. In thiscase, the piezoelectric element 120 is disposed on the upper side wallportion 119 b of two side wall portions 119 b continuously arrangedalong the above two sides. Here, the thickness of the side wall portion119 b provided with the piezoelectric element 120 is as small as that ofthe bottom surface portion 119 a, and hence vibration generated in thepiezoelectric element 120 is efficiently transmitted to the bottomsurface portion 119 a, whereby strong vibration having a high vibrationspeed can be generated in the bottom surface portion 119 a. It is to benoted that here, short and long sides of a virtual rectangle 176 in FIG.10 substantially correspond to short and long sides of the bottomsurface portion 119 a as shown in the drawing.

Note that it has been described that a material of the dust filter 119is transparent glass, but the material may be a resin such as amethacrylic methyl resin or a polycarbonate resin. A resin or glassmaterial which enables forming is optimum.

A method of removing dust will be explained in detail, with reference toFIG. 11. FIG. 11 shows a cross section identical to that shown in FIG.4B. Assume that the piezoelectric element 120 is polarized in thedirection of arrow 177 as shown in FIG. 11. If a voltage of a specificfrequency is applied to the piezoelectric element 120 at a certain timeto, the vibrator 170 will be deformed as indicated by solid lines. Atthe mass point Y existing at given position y in the surface of thevibrator 170, the vibration z in the Z-direction is expressed byEquation 2, as follows:

z=A·sin(Y)·cos(ωt)  (2)

where ω is the angular velocity of vibration, A is the amplitude ofvibration in the Z-direction, and Y=2 πy/λ (λ: wavelength of bendingvibration).

The Equation 2 represents the standing-wave vibration shown in FIG. 4A.Thus, if y=s·λ/2 (here, is an integer), then Y=sπ, and sin(Y)=0. Hence,a node 178, at which the amplitude of vibration in the Z-direction iszero irrespective of time, exists for every π/2. This is standing-wavevibration. The state indicated by broken lines in FIG. 11 takes place ift=kπ/ω (k is odd), where the vibration assumes a phase opposite to thephase at time t₀.

Vibration z(Y₁) at point Y₁ on the dust filter 119 is located at anantinode 179 of standing wave, bending vibration. Hence, the vibrationin the Z-direction has amplitude A, as expressed in Equation 3, asfollows:

z(Y ₁)=A·cos(ωt)  (3)

If Equation 3 is differentiated with time, the vibration speed Vz(Y₁) atpoint Y₁ is expressed by Equation 4, below, because ω=2πf, where f isthe frequency of vibration:

$\begin{matrix}{{{Vz}\left( Y_{1} \right)} = {\frac{\left( {z\left( Y_{1} \right)} \right)}{t} = {{- 2}\pi \; {f \cdot A \cdot {\sin \left( {\omega \; t} \right)}}}}} & (4)\end{matrix}$

If Equation 4 is differentiated with time, vibration acceleration αz(Y₁)is expressed by Equation 5, as follows:

$\begin{matrix}{{\alpha \; {z\left( Y_{1} \right)}} = {\frac{\left( {{Vz}\left( Y_{1} \right)} \right)}{t} = {{- 4}\pi^{2}{f^{2} \cdot A \cdot {\cos \left( {\omega \; t} \right)}}}}} & (5)\end{matrix}$

Therefore, the dust 180 adhering at point Y₁ receives the accelerationof Equation 5. The inertial force Fk the dust 180 receives at this timeis given by Equation 6, as follows:

Fk=αz(Y ₁)·M=−4π² f ² ·A·cos(ωt)·M  (6)

where M is the mass of the dust 180.

As can be seen from Equation 6, the inertial force Fk increases asfrequency f is raised, in proportion to the square of f. However, theinertial force cannot be increased if amplitude A is small, no matterhow much frequency f is raised. Generally, kinetic energy of vibrationcan be produced, but in a limited value, if the piezoelectric element120 that produces the kinetic energy has the same size. Therefore, ifthe frequency is raise in the same vibrational mode, vibrationalamplitude A will change in inverse proportion to the square of frequencyf. Even if the resonance frequency is raised to achieve a higher-orderresonance mode, the vibrational frequency will fall, not increasing thevibration speed or the vibration acceleration. Rather, if the frequencyis raised, ideal resonance will hardly be accomplished, and the loss ofvibrational energy will increase, inevitably decreasing the vibrationacceleration. That is, the mode cannot attain large amplitude if thevibration is produced in a resonance mode that uses high frequency only.The dust removal efficiency will be much impaired.

Although the dust filter 119 is rectangular, the peak ridges 174 ofvibrational amplitude form closed loops around the optical axis in thevibrational mode of the embodiment, which is shown in FIG. 4A. In thevibrational mode of the embodiment, which is shown in FIG. 5, the peakridges 174 of vibrational amplitude form curves surrounding the midpointof each side. The wave reflected from the side extending in theX-direction and the wave reflected from the side extending in theY-direction are efficiently synthesized, forming a standing wave. On theother hand, in the vibrational mode of FIG. 4A, the maximum vibrationspeed around the center of the area which spreads from the center of thedust filter 119 and through which the object light passes is largest. Inthe vibrational mode of FIG. 5, the maximum vibration speed of the abovecenter lowers from about 50% to 70% of that in the vibrational mode ofFIG. 4A. Even in the vibrational mode of FIG. 5, however, the maximumvibration speed of the center is larger than that in the conventionalrectangular flat plate.

In vibration wherein the peak ridges 174 of vibrational amplitude formclosed loops around the optical axis or the peak ridges 174 form curvessurrounding the midpoint of each side, the dust filter 119 can undergovibration of amplitude a similar to that of concentric vibration thatmay occur if the dust filter 119 has a disc shape. In any vibrationalmode in which the amplitude is simply parallel to the side, thevibration acceleration is only 10% or more of the acceleration achievedin this embodiment.

In the vibration wherein the peak ridges 174 of vibrational amplitudeform closed loops or curves surrounding the midpoint of each side, thevibrational amplitude is the largest at the center of the vibrator 170and small at the closed loop or the curve at circumferential edges.Thus, the dust removal capability is maximal at the center of the image.If the center of the vibrator 170 is aligned with the optical axis, theshadow of dust 180 will not appear in the center part of the image,which has high image quality. This is an advantage.

In the vibration node areas 173, which exist in the focusing-beampassing area 149, the nodes 178 may be changed in position by changingthe drive frequencies of the piezoelectric element 120. Then, theelement 120 resonates in a different vibrational mode, whereby the dustcan be removed, of course.

The prescribed frequency at which to vibrate the piezoelectric element120 is determined by the shape and dimensions of the dust filter 119 andpiezoelectric element 120 forming the oscillator 170, and the materialsand supported states of them. Therefore, it is desirable to measure thetemperature of the vibrator 170 and to consider the change in thenatural frequency of the vibrator 170, before the vibrator 170 is used.A temperature sensor (not shown) is therefore connected to a temperaturemeasuring circuit (not shown), in the digital camera 10. The value bywhich to correct the vibrational frequency of the vibrator 170 inaccordance with the temperature detected by the temperature sensor isstored in the nonvolatile memory 128. Then, the measured temperature andthe correction value are read into the Bucom 101. The Bucom 101calculates a drive frequency, which is used as drive frequency of thedust filter control circuit 121. Thus, vibration can be produced, whichis efficient with respect to temperature changes, as well.

The dust filter control circuit 121 of the digital camera 10 accordingto this invention will be described below, with reference to FIGS. 12and 13. The dust filter control circuit 121 has such a configuration asshown in FIG. 12. The components of the dust filter control circuit 121produce signals (Sig1 to Sig4) of such waveforms as shown in the timingchart of FIG. 13. These signals will control the dust filter 119, aswill be described below.

More specifically, as shown in FIG. 12, the dust filter control circuit121 comprises a N-scale counter 183, a half-frequency dividing circuit184, an inverter 185, a plurality of MOS transistors Q₀₀, Q₀₁ and Q₀₂, atransformer 186, and a resistor R₀₀.

The dust filter control circuit 121 is so configured that a signal(Sig4) of the prescribed frequency is produced at the secondary windingof the transformer 186 when MOS transistors Q₀₁ and Q₀₂ connected to theprimary winding of the transformer 186 are turned on and off. The signalof the prescribed frequency drives the piezoelectric element 120,thereby causing the vibrator 170, to which the dust filter 119 issecured, to produce a resonance standing wave.

The Bucom 101 has two output ports P_PwCont and D_NCnt provided ascontrol ports, and a clock generator 187. The output ports P_PwCont andD_NCnt and the clock generator 187 cooperate to control the dust filtercontrol circuit 121 as follows. The clock generator 187 outputs a pulsesignal (basic clock signal) having a frequency much higher than thefrequency of the signal that will be supplied to the piezoelectricelement 120. This output signal is signal Sig1 that has the waveformshown in the timing chart of FIG. 13. The basic clock signal is input tothe N-scale counter 183.

The N-scale counter 183 counts the pulses of the pulse signal. Everytime the count reaches a prescribed value “N,” the N-scale counter 183produces a count-end pulse signal. Thus, the basic clock signal isfrequency-divided by N. The signal the N-scale counter 183 outputs issignal Sig2 that has the waveform shown in the timing chart of FIG. 13.

The pulse signal produced by means of frequency division does not have aduty ratio of 1:1. The pulse signal is supplied to the half-frequencydividing circuit 184. The half-frequency dividing circuit 184 changesthe duty ratio of the pulse signal to 1:1. The pulse signal, thuschanged in terms of duty ratio, corresponds to signal Sig3 that has thewaveform shown in the timing chart of FIG. 13.

While the pulse signal, thus changed in duty ratio, is high, MOStransistor Q₀₁ to which this signal has been input is turned on. In themeantime, the pulse signal is supplied via the inverter 185 to MOStransistor Q₀₂₋. Therefore, while the pulse signal (signal Sig3) is lowstate, MOS transistor Q₀₂ to which this signal has been input is turnedon. Thus, the transistors Q₀₁ and Q₀₂, both connected to the primarywinding of the transformer 186, are alternately turned on. As a result,a signal Sig4 of such frequency as shown in FIG. 13 is produced in thesecondary winding of the transformer 186.

The winding ratio of the transformer 186 is determined by the outputvoltage of the power-supply circuit 135 and the voltage needed to drivethe piezoelectric element 120. Note that the resistor R₀₀ is provided toprevent an excessive current from flowing in the transformer 186.

In order to drive the piezoelectric element 120, MOS transistor Q₀₀ mustbe on, and a voltage must be applied from the power-supply circuit 135to the center tap of the transformer 186. In this case, MOS transistorQ₀₀ is turned on or off via the output port P_PwCont of the Bucom 101.Value “N” can be set to the N-scale counter 183 from the output portD_NCnt of the Bucom 101. Thus, the Bucom 101 can change the drivefrequency for the piezoelectric element 120, by appropriatelycontrolling value “N.”

The frequency can be calculated by using Equation 7, as follows:

$\begin{matrix}{{fdrv} = \frac{fpls}{2N}} & (7)\end{matrix}$

where N is the value set to the N-scale counter 183, fpls is thefrequency of the pulse output from the clock generator 187, and fdrv isthe frequency of the signal supplied to the piezoelectric element 120.

The calculation based on Equation 7 is performed by the CPU (controlunit) of the Bucom 101.

If the dust filter 119 is vibrated at a frequency in the ultrasonicregion (i.e., 20 kHz or more), the operating state of the dust filter119 cannot be aurally discriminated, because most people cannot hearsound falling outside the range of about 20 to 20,000 Hz. This is whythe operation display LCD 129 or the operation display LED 130 has adisplay unit for showing how the dust filter 119 is operating, to theoperator of the digital camera 10. More precisely, in the digital camera10, the vibrating members (piezoelectric element 120) imparts vibrationto the dust-screening member (dust filter 119) that is arranged in frontof the CCD 117, can be vibrated and can transmit light. In the digitalcamera 10, the display unit is operated in interlock with the vibratingmember drive circuit (i.e., dust filter control circuit 121), thusinforming how the dust filter 119 is operating (later described indetail).

To explain the above-described characteristics in detail, the controlthe Bucom 101 performs will be described with reference to FIGS. 14A to18. FIGS. 14A and 14B show the flowchart that relates to the controlprogram, which the Bucom 101 starts executing when the power switch (notshown) provided on the body unit 100 of the camera 10 is turned on.

First, a process is performed to activate the digital camera 10 (StepS101). That is, the Bucom 101 controls the power-supply circuit 135. Socontrolled, the power-supply circuit 135 supplies power to the othercircuit units of the digital camera 10. Further, the Bucom 101initializes the circuit components.

Next, the Bucom 101 calls a sub-routine “silent vibration,” vibratingthe dust filter 119, making no sound (that is, at a frequency fallingoutside the audible range) (Step S102). The “audible range” ranges fromabout 200 to 20,000 Hz, because most people can hear sound fallingwithin this range.

Steps S103 to S124, which follow, make a group of steps that iscyclically repeated. That is, the Bucom 101 first detects whether anaccessory has been attached to, or detached from, the digital camera 10(Step S103). Whether the lens unit 200 (i.e., one of accessories), forexample, has been attached to the body unit 100 is detected. Thisdetection, e.g., attaching or detaching of the lens unit 200, isperformed as the Bucom 101 communicates with the Lucom 201.

If a specific accessory is detected to have been attached to the bodyunit 100 (YES in Step S104), the Bucom 101 calls a subroutine “silentvibration” and causes the dust filter 119 to vibrate silently (StepS105).

While an accessory, particularly the lens unit 200, remains not attachedto the body unit 100 that is the camera body, dust is likely to adhereto each lens, the dust filter 119, and the like. It is thereforedesirable to perform an operation of removing dust at the time when itis detected that the lens unit 200 is attached to the body unit 100. Itis highly possible that dust adheres as the outer air circulates in thebody unit 100 at the time a lens is exchanged with another. It istherefore advisable to remove dust when a lens is exchange with another.Then, it is determined that photography will be immediately performed,and the operation goes to Step S106.

If a specific accessory is not detected to have been attached to thebody unit 100 (NO in Step S104), the Bucom 101 goes to the next step,i.e., Step S106.

In Step S106, the Bucom 101 detects the state of a specific operationswitch that the digital camera 10 has.

That is, the Bucom 101 determines whether the first release switch (notshown), which is a release switch, has been operated from the on/offstate of the switch (Step S107). The Bucom 101 reads the state. If thefirst release switch has not been turned on for a predetermined time,the Bucom 101 discriminates the state of the power switch (Step S108).If the power switch is on, the Bucom 101 returns to Step S103. If thepower switch is off, the Bucom 101 performs an end-operation (e.g.,sleep).

On the other hand, the first release switch may be found to have beenturned on in Step S107. In this case, the Bucom 101 acquires theluminance data about the object from the acquired image from the imageprocess controller 126, and calculates from this data an exposure time(Tv value) and a diaphragm value (Av value) that are optimal for theimage acquisition unit 116 and lens unit 200, respectively (Step S109).

Thereafter, the Bucom 101 detects the contrast of the acquired image(step S110). The Bucom 101 then determines whether the detected contrastfalls within a tolerance range (step S111). If the contrast does notfall within the tolerance range, the Bucom 101 drives the photographiclens 202 (step S112) and returns to step S103.

On the other hand, the contrast may falls within the tolerance range. Inthis case, the Bucom 101 calls the subroutine “silent vibration” andcauses the dust filter 119 to vibrate silently (step S113).

Further, the Bucom 101 determines whether the second release switch (notshown), which is another release switch, has been operated (Step S114).If the second release switch is on, the Bucom 101 goes to Step S115 andstarts the prescribed photographic operation (later described indetail). If the second release switch is off, the Bucom 101 returns toStep S108.

During the image acquisition operation, the electronic image acquisitionis controlled for a time that corresponds to the preset time forexposure (i.e., exposure time), as in ordinary photography.

As the above-mentioned photographic operation, Steps S115 to S121 areperformed in a prescribed order to photograph an object. First, theBucom 101 transmits the Av value to the Lucom 201, instructing the Lucom201 to drive the diaphragm 203 (Step S115). Then, the Bucom 101 causesthe front curtain of the shutter 108 to start running, performing opencontrol (Step S117). Further, the Bucom 101 makes the image processcontroller 126 perform “image acquisition operation” (Step S118). Whenthe exposure to the CCD 117 (i.e., photography) for the timecorresponding to the Tv value ends, the Bucom 101 causes the rearcurtain of the shutter 108 to start running, achieving CLOSE control(Step S119). Then, the Bucom 101 cocks the shutter 108 (Step S120).

Then, the Bucom 101 instructs the Lucom 210 to move the diaphragm 203back to the open position (Step S121). Thus, a sequence of imageacquisition steps is terminated.

Next, the Bucom 101 determines whether the recording medium 127 isattached to the body unit 100 (Step S122). If the recording medium 127is not attached, the Bucom 101 displays an alarm (Step S123). The Bucom101 then returns to Step S103 and repeats a similar sequence of steps.

If the recording medium 127 is attached, the Bucom 101 instructs theimage process controller 126 to record the image data acquired byphotography, in the recording medium 127 (Step S124). When the imagedata is completely recorded, the Bucom 101 returns to Step S103 againand repeats a similar sequence of steps.

In regard to the detailed relation between the vibration state and thedisplaying state will be explained in detail, the sequence ofcontrolling the “silent vibration” subroutine will be explained withreference to FIGS. 15 to 18. The term “vibration state” means the stateof the vibration induced by the piezoelectric element 120, i.e.,vibrating members. FIG. 19 shows the form of a resonance-frequency wavethat is continuously supplied to the vibrating members during silentvibration. The subroutine of FIG. 15, i.e., “silent vibration,” and thesubroutine of FIGS. 16 to 18, i.e., “display process” are routines foraccomplishing vibration exclusively for removing dust from the dustfilter 119. Vibrational frequency f₀ is set to a value close to theresonance frequency of the dust filter 119. In the vibrational mode ofFIG. 4A, for example, the vibrational frequency is 44 kHz, higher thanat least 20 kHz, and produces sound not audible to the user.

As shown in FIG. 15, when the “silent vibration” is called, the Bucom101 first reads the data representing the drive time (Toscf0) and drivefrequency (resonance frequency: Noscf0) from the data stored in aspecific area of the nonvolatile memory 128 (Step S201). At this timing,the Bucom 101 causes the display unit provided in the operation displayLCD 129 or operation display LED 130 to turn on the vibrational modedisplay, as shown in FIG. 16 (Step S301). The Bucom 101 then determineswhether a predetermined time has passed (Step S302). If thepredetermined time has not passed, the Bucom 101 makes the display unitkeep turning on the vibrational mode display. Upon lapse of thepredetermined time, the Bucom 101 turns off the displaying of thevibrational mode display (Step S303).

Next, the Bucom 101 outputs the drive frequency Noscf0 from the outputport D_NCnt to the N-scale counter 183 of the dust filter controlcircuit 121 (Step S202).

In the following steps S203 to S205, the dust is removed as will bedescribed below. First, the Bucom 101 sets the output port P_PwCont toHigh, thereby starting the dust removal (Step S203). At this timing, theBucom 101 starts displaying the vibrating operation as shown in FIG. 17(Step S311). The Bucom 101 then determines whether or not thepredetermined time has passed (Step S312). If the predetermined time hasnot passed, the Bucom 101 keeps displaying the vibrating operation. Uponlapse of the predetermined time, the Bucom 101 stops displaying of thevibrating operation (Step S313). The display of the vibrating operation,at this time, changes as the time passes or as the dust is removed (howit changes is not shown, though). The predetermined time is almost equalto Toscf0, i.e., the time for which the vibration (later described)continues.

If the output port P_PwCont is set to High in Step S203, thepiezoelectric element 120 vibrates the dust filter 119 at the prescribedvibrational frequency (Noscf0), removing the dust 180 from the surfaceof the dust filter 119. At the same time the dust 180 is removed fromthe surface of the dust filter 119, air is vibrated, producing anultrasonic wave. The vibration at the drive frequency Noscf0, however,does not make sound audible to most people. Hence, the user hearsnothing. The Bucom 101 waits for the predetermined time Toscf0, whilethe dust filter 119 remains vibrated (Step S204). Upon lapse of thepredetermined time Toscf0, the Bucom 101 sets the output port P_PwContto Low, stopping the dust removal operation (Step S205). At this timing,the Bucom 101 turns on the display unit, whereby the displaying of thevibration-end display is turned on (Step S321). When the Bucom 101determines (in Step S322) that the predetermined time has passed, thedisplaying of the vibration-end display is turned off (Step S323). TheBucom 101 then returns to the step next to the step in which the “silentvibration” is called.

The vibrational frequency f₀ (i.e., resonance frequency Noscf0) and thedrive time (Toscf0) used in this subroutine define such a waveform asshown in the graph of FIG. 19. As can be seen from this waveform,constant vibration (f₀=44 kHz) continues for a time (i.e., Toscf0) thatis long enough to accomplish the dust removal.

That is, the vibrational mode adjusts the resonance frequency applied tothe vibrating member, controlling the dust removal.

Second Embodiment

The subroutine “silent vibration” called in the camera sequence (mainroutine) that the Bucom performs in a digital camera that is a secondembodiment of the image equipment according to this invention will bedescribed with reference to FIG. 20. FIG. 20 illustrates a modificationof the subroutine “silent vibration” shown in FIG. 15. The secondembodiment differs from the first embodiment in the operating mode ofthe dust filter 119. In the first embodiment, the dust filter 119 isdriven at a fixed frequency, i.e., frequency f₀, producing a standingwave. By contrast, in the second embodiment, the drive frequency isgradually changed, thereby achieving large-amplitude vibration atvarious frequencies including the resonance frequency, without strictlycontrolling the drive frequency.

Moreover, in the dust filter 119, there is an aspect ratio that thevibrational mode will greatly change (that is, the vibration speed ratiowill abruptly change) if the aspect ratio changes in the dust filter 119owing to fluctuations during the manufacture. Therefore, in the case ofthe dust filter 119 in which such an aspect ratio is present, it isnecessary to set a precise resonance frequency in each product and todrive the piezoelectric element 120 at the frequency. This is becausethe vibration speed further lowers, if the piezoelectric element isdriven at any frequency other than the resonance frequency. An extremelysimple control circuit configuration can, nonetheless, drive thepiezoelectric element precisely at the resonance frequency if thefrequency is controlled as in the second embodiment. A method of controlcan therefore be achieved to eliminate any difference in resonancefrequency between the products.

First, the Bucom 101 reads the data representing the drive time(Toscf0), drive-start frequency (Noscfs), frequency change value (Δf)and drive-end frequency (Noscft), from the data stored in a specificarea of the nonvolatile memory 128 (Step S211). At this timing, theBucom 101 causes the display unit to display the vibrational mode asshown in FIG. 16, in the same way as in the first embodiment.

Next, the Bucom 101 sets the drive-start frequency (Noscfs) as drivefrequency (Noscf) (Step S212). The Bucom 101 then outputs the drivefrequency (Noscf) from the output port D_NCnt to the N-scale counter 183of the dust filter control circuit 121 (Step S213).

In the following steps S214 et seq., the dust is removed as will bedescribed below. First, the dust removal is started. At this time, thedisplay of the vibrating operation is performed as shown in FIG. 17, asin the first embodiment.

First, the Bucom 101 sets the output port P_PwCont to High, to achievedust removal (Step S214). The piezoelectric element 120 vibrates thedust filter 119 at the prescribed vibrational frequency (Noscf),producing a standing wave of a small amplitude at the dust filter 119.The dust 180 cannot be removed from the surface of the dust filter 119,because the vibrational amplitude is small. This vibration continues forthe drive time (Toscf0) (Step S215). Upon lapse of this drive time(Toscf0), the Bucom 101 determines whether the drive frequency (Noscf)is equal to the drive-end frequency (Noscft) (Step S216). If the drivefrequency is not equal to the drive-end frequency (NO in Step S216), theBucom 101 adds the frequency change value (Δf) to the drive frequency(Noscf), and sets the sum to the drive frequency (Noscf) (Step S217).Then, the Bucom 101 repeats the sequence of Steps S212 to S216.

If the drive frequency (Noscf) is equal to the drive-end frequency(Noscft) (YES in Step S216), the Bucom 101 sets the output port P_PwContto Low, stopping the vibration of the piezoelectric element 120 (StepS218), thereby terminating the “silent vibration.” At this point, thedisplay of vibration-end is performed as shown in FIG. 18, as in thefirst embodiment.

As the frequency is gradually changed as described above, the amplitudeof the standing wave increases. In view of this, the drive-startfrequency (Noscfs), the frequency change value (Δf) and the drive-endfrequency (Noscft) are set so that the resonance frequency of thestanding wave may be surpassed. As a result, a standing wave of smallvibrational amplitude is produced at the dust filter 119. The standingwave can thereby controlled, such that its vibrational amplitudegradually increases until it becomes resonance vibration, and thendecreases thereafter. If the vibrational amplitude (corresponding tovibration speed) is larger than a prescribed value, the dust 180 can beremoved. In other words, the dust 180 can be removed while thevibrational frequency remains in a prescribed range. This range is broadin the present embodiment, because the vibrational amplitude is largeduring the resonance.

If the difference between the drive-start frequency (Noscfs) and thedrive-end frequency (Noscft) is large, the fluctuation of the resonancefrequency, due to the temperature of the vibrator 170 or to thedeviation in characteristic change of the vibrator 170, during themanufacture, can be absorbed. Hence, the dust 180 can be reliablyremoved from the dust filter 119, by using an extremely simple circuitconfiguration.

The present invention has been explained, describing some embodiments.Nonetheless, this invention is not limited to the embodiments describedabove. Various changes and modifications can, of course, be made withinthe scope and spirit of the invention.

For example, a mechanism that applies an air flow or a mechanism thathas a wipe may be used in combination with the dust removal mechanismhaving the vibrating member, in order to remove the dust 180 from thedust filter 119.

Moreover, in the above embodiments, a liquid crystal monitor is used aviewfinder. It is of course also possible to use a single-lens reflexcamera having an optical viewfinder.

In the embodiments described above, the CCD 117 is used as an imagesensor element. It is of course permitted to use a CMOS and other imagesensor. Further, in the embodiments, the vibrating member ispiezoelectric element 120. The piezoelectric element may be replaced byelectrostrictive member or super nagnetostrictive element. Furthermore,a plurality of vibrating members may be provided in peripheral portionsof the dust-screening member, so that the oscillation amplitude can begreater. The transparent part of the dust-screening member may notnecessarily be flat, but may be curved, for example, spherical.

In order to remove dust 180 more efficiently from the member vibrated,the member may be coated with an indium-tin oxide (ITO) film, which is atransparent conductive film, indium-zinc film, poly 3, 4 ethylenedioxythiophene film, surfactant agent film that is a hygroscopicanti-electrostatic film, siloxane-based film, or the like. In this case,the frequency, the drive time, etc., all related to the vibration, areset to values that accord with the material of the film.

Moreover, the optical LPF 118, described as one embodiment of theinvention, may be replaced by a plurality of optical LPFs that exhibitbirefringence. Of these optical LPFs, the optical LPF located closest tothe object of photography may be used as a dust-screening member (i.e.,a subject to be vibrated), in place of the dust filter 119 shown in FIG.2A.

Further, a camera may does not have the optical LPF 118 of FIG. 2Adescribed as one embodiment of the invention, and the dust filter 119may be used as an optical element such as an optical LPF, aninfrared-beam filter, a deflection filter, or a half mirror.

Furthermore, the camera may not have the optical LPF 118, and the dustfilter 119 may be replaced by the protection glass plate 142 shown inFIG. 2A. In this case, the protection glass plate 142 and the CCD chip136 remain free of dust and moisture, and the structure of FIG. 2A thatsupports and yet vibrates the dust filter 119 may be used to support andvibrate the protection glass plate 142. Needless to say, the protectionglass plate 142 may be used as an optical element such as an opticalLPF, an infrared-beam filter, a deflection filter, or a half mirror.

Furthermore, the holding member 151 does not have to have an L-shapedsection shown in FIG. 2A, and may have a constitution of a plate-likemember surrounding an opening of the holder 145 which becomes the imageforming light passing area 149, in the form of a picture frame. In thiscase, the plate-like holding member is fixed to the holder 145 with theadhesive or the like on the surface thereof which is orthogonal to thefitting portion 150, and around the whole periphery of the surface ofthe member which faces the fixing surface, there is formed the groove152 in which the open end 119 d of the dust filter 119 fits.

The image equipment according to this invention is not limited to theimage acquisition apparatus (digital camera) exemplified above. Thisinvention can be applied to any other apparatus that needs a dustremoval function. The invention can be practiced in the form of variousmodifications, if necessary. More specifically, a dust moving mechanismaccording to this invention may be arranged between the display elementand the light source or image projecting lens in an image projector.

Additional advantages and modifications will readily occur to thoseskilled in the art. Therefore, the invention in its broader aspects isnot limited to the specific details and representative embodiments shownand described herein. Accordingly, various modifications may be madewithout departing from the spirit or scope of the general inventiveconcept as defined by the appended claims and their equivalents.

What is claimed is:
 1. A vibrating device comprising: a dust-screeningmember disposed in front of an image surface of an image forming elementhaving the image surface in which an optical image is generated, thedust-screening member having a box shape with about the same small platethickness as a whole, and including, in a bottom surface portion of thebox shape, a transparent part which spreads from the center of thebottom surface portion; and a vibrating member disposed outside thetransparent part of the dust-screening member and configured togenerate, in the bottom surface portion of the dust-screening member,vibration having a vibrational amplitude which is vertical to the bottomsurface portion thereof.
 2. The device according to claim 1, wherein thedust-screening member has an open end of the box shape fixed to a fixingmember.
 3. The device according to claim 1, wherein the dust-screeningmember has an open end of the box shape fixed to a fixing member via asoft holding member.
 4. The device according to claim 1, wherein thedust-screening member has at least one flat surface which forms the boxshape, and the vibrating member is fixed to the flat surface.
 5. Thedevice according to claim 1, wherein the vibrating member is apiezoelectric element.
 6. The device according to claim 5, furthercomprising: a drive section configured to apply, to the piezoelectricelement every predetermined time, a frequency signal which includes afrequency determined in accordance with a dimension and a material ofthe dust-screening member and which changes every determined transitionfrequency from a start frequency to an end frequency.
 7. An imageequipment comprising: an image forming element having an image surfacein which an optical image is generated; a dust-screening member disposedin front of the image surface of the image forming element, thedust-screening member having a box shape with about the same small platethickness as a whole, and including, in a bottom surface portion of thebox shape, a transparent part which spreads from the center of thebottom surface portion; a vibrating member disposed outside thetransparent part of the dust-screening member and configured togenerate, in the bottom surface portion of the dust-screening member,vibration having a vibrational amplitude which is vertical to the bottomsurface portion thereof; and a sealing structure portion configured toseal a space portion on the side of circumferential edges of the imageforming element and the dust-screening member and to constitute thesealed space portion in a portion where both the image forming elementand the dust-screening member are formed to face each other.
 8. Theequipment according to claim 7, wherein the sealing structure portionincludes: a holder configured to receive the image forming element; anda holding member configured to airtightly hold betweenness of an openend of the dust-screening member having the box shape and the holder. 9.A vibrating device comprising: a dust-screening member disposed in frontof an image surface of an image forming element having the image surfacein which an optical image is generated, the dust-screening member beingconfigured to have a box shape which includes a bottom surface portionhaving a light transmitting part through which one of light coming fromthe image forming element and light coming into the image formingelement transmits, and side wall portions which tilt as much as apredetermined angle and extend from all end face portions of the bottomsurface portion in a direction of the image forming element, and isformed so that at least the bottom surface portion has a substantiallyuniform small thickness; and a vibrating member disposed in one of aposition of the dust-screening member other than the light transmittingpart of the bottom surface portion and a flat surface portion of theside wall portion, and configured to apply, to the bottom surfaceportion of the dust-screening member, a vibrational amplitude which isvertical to the bottom surface portion thereof.
 10. The device accordingto claim 9, wherein the dust-screening member has the side wall portionsfixed to a fixing member via a soft holding member.
 11. The deviceaccording to claim 9, wherein the bottom surface portion of thedust-screening member has at least one linear side, and the vibratingmember is fixed to the side wall portion including the linear side. 12.The device according to claim 9, wherein the bottom surface portion ofthe dust-screening member has an oval shape, and the vibrating member isfixed along an outer periphery of the oval shape.
 13. An image equipmentcomprising: an image forming unit including an image forming elementhaving an image surface in which an optical image is generated; adust-screening member disposed in front of an image surface of the imageforming element, the dust-screening member being configured to have abox shape which includes a bottom surface portion having a lighttransmitting part through which one of light coming from the imageforming element and light coming into the image forming elementtransmits, and side wall portions which tilt as much as a predeterminedangle and extend from all end face portions of the bottom surfaceportion in a direction of the image forming element, and is formed sothat at least the bottom surface portion has a substantially uniformsmall thickness; a vibrating member disposed in one of a position of thedust-screening member other than the light transmitting part of thebottom surface portion and a flat surface portion of the side wallportion, and configured to apply, to the bottom surface portion of thedust-screening member, a vibrational amplitude which is vertical to thebottom surface portion thereof; and a sealing structure portionconfigured to constitute a sealed space portion in a portion where boththe image forming unit and the dust-screening member are formed to faceeach other.